A. Field of the Invention
The device of the present invention generally relates to apparatus for protecting electrical equipment, circuits and systems from damage or destruction due to overvoltage surges, commonly referred to as surge protectors, and, more particularly, to a valve-type surge protector for protecting relatively low voltage or secondary equipment, circuits and systems.
B. Description of the Prior Art
A surge protector or arrester is commonly electrically connected across a comparatively expensive piece of electrical equipment to shunt overvoltage surges, for example, overvoltage surges due to lightning strokes, to ground to thereby protect the piece of electrical equipment and the circuit from damage or destruction.
Secondary surge protectors are presently available in several different types and sizes depending upon the voltage rating of the specific secondary circuit, piece of equipment or system to be protected. One particular type of secondary surge protector is rated at 175 and 75 volts A.C or 125 volts D.C. and is designed to pass surge currents up to ten thousand amperes to ground. This secondary surge protector is especially adapted to protect a 120/240 volt A.C. circuit, equipment and system.
In this particular secondary surge protector, the spark gap and valve block assemblies, contacts, and three insulated leads are assembled and secured together as a unit outside of the surge protector housing. The entire unit is then mounted in a generally vertical position within the circular housing, with its three leads extending through and directed from the bottom of the housing. An attempt is then made to insulate the exposed conductive portions of the contacts associated with the leads, and to seal the entrance of the leads to the housing, by the application of a sealing and insulating compound over the exposed portions, generally inaccessibly disposed under the unit.
Since the entire unit is mounted in the housing prior to the application of the sealing and insulating compound to the exposed portions, often all of the exposed portions are not fully covered or insulated by the sealing and insulating compound. The relatively closely spaced exposed and noninsulated contact portions result in a reduced capacity of the surge protector to shunt relatively high surge currents to ground without flashover between the exposed portions. Additionally, moisture entering the units at the unsealed portions can also cause flashover and destruction of the unit.